Bulk-acoustic wave resonator

Abstract

A bulk-acoustic wave resonator includes: a substrate; a first electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the first electrode; a second electrode disposed to cover at least a portion of the piezoelectric layer; a metal pad connected to the first electrode and the second electrode; and a connection member connected an upper surface of the metal pad. A lower end portion of the connection member includes a tapered portion decreasing in a diameter in a direction toward a lower end of the connection member, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°.

What is claimed is: 
     
       1. A bulk-acoustic wave resonator, comprising:
 a substrate; 
 a first electrode disposed on the substrate; 
 a piezoelectric layer disposed to cover at least a portion of the first electrode; 
 a second electrode disposed to cover at least a portion of the piezoelectric layer; 
 a metal pad connected to the first electrode and the second electrode; and 
 a connection member connected an upper surface of the metal pad, 
 wherein an upper end portion of the connection member includes a cylindrical portion having a constant diameter, 
 wherein a lower end portion of the connection member includes a tapered portion disposed below the cylindrical portion and decreasing in a diameter in a direction toward the lower end of the connection member, 
 wherein an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°, and 
 wherein a diameter of a bottom surface of the tapered portion is 60 μm or more. 
 
     
     
       2. A bulk-acoustic wave resonator, comprising:
 a substrate; 
 a first electrode disposed on the substrate; 
 a piezoelectric layer disposed to cover at least a portion of the first electrode; 
 a second electrode disposed to cover at least a portion of the piezoelectric layer; 
 a metal pad connected to the first electrode and the second electrode; and 
 a connection member connected an upper surface of the metal pad, 
 wherein a lower end portion of the connection member includes a tapered portion decreasing in a diameter in a direction toward the lower end of the connection member, the tapered portion has a height of 6 μm or more, and an angle between an inclined surface of the tapered portion and the upper surface of the metal pad is 45° to 80°. 
 
     
     
       3. The bulk-acoustic wave resonator of  claim 2 , wherein an upper end portion of the connection member includes a cylindrical portion having a constant diameter, and wherein the tapered portion is disposed below the cylindrical portion. 
     
     
       4. The bulk-acoustic wave resonator of  claim 3 , wherein a diameter of a bottom surface of the tapered portion is 60 μm or more. 
     
     
       5. The bulk-acoustic wave resonator of  claim 2 , wherein the connection member is made of any one of gold (Au), a gold-tin (Au—Sn) alloy, copper (Cu), a copper-tin (Cu—Sn) alloy, and aluminum (Al), and an aluminum alloy, or a material containing any two or more of gold (Au), a gold-tin (Au—Sn) alloy, copper (Cu), a copper-tin (Cu—Sn) alloy and aluminum (Al), and an aluminum alloy. 
     
     
       6. The bulk-acoustic wave resonator of  claim 2 , further comprising an insertion layer disposed between the first electrode and the piezoelectric layer. 
     
     
       7. The bulk-acoustic wave resonator of  claim 2 , further comprising a membrane layer forming a cavity together with the substrate. 
     
     
       8. The bulk-acoustic wave resonator of  claim 7 , further comprising:
 an etch stop portion disposed to surround the cavity; and 
 a sacrificial layer disposed to surround the etch stop portion. 
 
     
     
       9. The bulk-acoustic wave resonator of  claim 7 , wherein the membrane layer comprises an inclined portion disposed obliquely with respect to an upper surface of the substrate, and a flat portion disposed in an active region in which the first electrode, the piezoelectric layer, and the second electrode all overlap one another. 
     
     
       10. The bulk-acoustic wave resonator of  claim 9 , wherein the second electrode includes a frame disposed at an edge of the active region, and wherein the frame has a thickness greater than a thickness of a remainder of the second electrode. 
     
     
       11. The bulk-acoustic wave resonator of  claim 7 , further comprising an insulating layer disposed on the substrate, below the cavity. 
     
     
       12. The bulk-acoustic wave resonator of  claim 2 , wherein the metal pad comprises a first metal pad connected to the first electrode, and a second metal pad connected to the second electrode. 
     
     
       13. A bulk-acoustic wave resonator, comprising:
 a substrate; 
 a first electrode disposed on the substrate; 
 a piezoelectric layer disposed to cover at least a portion of the first electrode; 
 a second electrode disposed to cover at least a portion of the piezoelectric layer; 
 a metal pad connected to the first electrode and the second electrode; and 
 a connection member connected to an upper surface of the metal pad, 
 wherein the connection member comprises:
 a cylindrical portion disposed at an upper end portion of the connection member and having a constant diameter; and 
 a tapered portion disposed below the cylindrical portion, the tapered portion having a height of 6 μm or more and a diameter that is smaller at a lower end of the tapered portion than an upper end of the tapered portion. 
 
 
     
     
       14. The bulk acoustic wave resonator of  claim 13 , wherein a bottom surface of the tapered portion is in contact with the upper surface of the metal pad. 
     
     
       15. The bulk acoustic wave resonator of  claim 14 , wherein a diameter of the bottom surface of the tapered portion is 60 μm or more.